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Can you fly 2000 miles on an engine that costs less than $500k? If so, what type of engine?
Ok so Im exploring ways to bring cargo and medical supplies to various rural cities in say Africa without relying on ground infrastructure. Just short and cheap runways spread around the continent. It seems any type of VTOL plane wouldn't have the range. Electric is also out. It also seems like piston planes don't have the range, while turbojets are millions of dollars. What about used turbojets? Whats stopping piston engines from flying longer?

You are unable to stop and refuel somewhere in 2000 miles? Is this the "round trip" range? Typically piston planes like Caravans don't have bathrooms, so for the sake of your pilots/crew you will probably have to stop somewhere in there anyway.

Caravans aren't piston powered.  I don't know Africa, but I know a missionary pilot who flew there most of his life.  I think there are already lots of short cheap runways around the continent that serve rural bush villages.  And bush flying in places like Alaska is similarly well established.  Your 2000 mile range requirement will be tough to meet, but I don't think you have to.  Unless this is some brand new "market"?

Sorry! I meant unmanned plane

Then there are none... Not commercially available at least, and certainly not under $500K.

Well Im talking about a concept plane for a competition. I just want to know if its possible with modern technology so I can design some sort of concept around this.

The engine isn't the limiting factor in range, it is fuel.

Your best bet would be an airplane/drone that is built from carbon composite and graphlite rod (pull-truded carbon rod with incredible strength - widely used in sailplane spars) powered by a couple of aviation diesels like the Austro Engine E4.
The Specific Fuel Consumption of the E4 is .336 lbs/hp/hr.  Except for similar competing diesels, nothing in any traditional aircraft engine configuration comes close except the old tubro-compound mechanical-monstrosity radials like the R3350 that could get into the high 3s (normal gas piston engines are around .45 lb/hp/hr and turboprops well above that, around .5-.6 lbs/hp/hr).
The E4 is 168 Hp so two would give you 336 HP for take off, and the engine burns 5 US Gal per side at 60% cruise, or 30 lbs per side, so to go 2000 nm, if you can get the thing to cruise at 150kt, you need 130 US Gal capacity plus a VFR reserve, say 140 gal total, or 840 lbs of fuel.
So design an airframe that can haul, say, a thousand pounds of payload with those two engines and 840 lbs of kerosene, and is clean enough to go 150kt, and there you have it.

Divide your SFCs by 10 and you're correct. Otherwise the E4 would cruise at 50 GPH, not 5. The rescaled SFCs then also agree with Jane's numbers, as verified with data from 500 entries in the ten CAFE flight efficiency races in the 1980s.

Oops decimal place finger trouble.  Thanks for pointing it out.

It's perfectly possible to build piston-engined planes with ranges of 2000 miles or more, for instance many WWII planes like the B-17 and B-29, pre-jet airliners like the Lockheed Constellation, or the Rutan Voyager.  The reason there are few, if any, in service today is that there is no real market.  Jets have taken the long-range commercial market, and pilots of smaller planes generally don't want to go that far without stopping for bathroom breaks.
If you are looking to design an unpiloted plane, the problem becomes even easier.  You should be able to use modern, non-certified engines derived from the automotive market, can fly at efficient speeds, and don't have to worry about breaks.

This is perhaps not going to be a very good answer to the specific question, but the mission you describe would constitute some out-of-the-box thinking.
As John K already suggested, a very light construction, perhaps in the spirit of Rutan Voyager suggested by Jamesqf would be a good starting point. Large wingspan to get efficient wings would give the chance to use less powerfull and/or exotic engines. John K's example of Austros is a good one.
In my mind what you should design is a motorglider on steroids. Relatively large cargo would otherwise require a lot of thrust, but you could compensate with wingspan and 2 or even three lifting surfaces.
Leaving the pilot out would save at least 400 lbs of weight (pilot, seat, controls, gauges and such), plus you would not need any pressurising, so you could fly ballistic profile flights: high power ascents (but not that steep as exess thrust is not great with full cargo), and the gliding the rest of the way. You could even feather the props and shut down the engine -> no cruise consumption (piston engines typically are not very efficient when operating in partial load = cruise).
I don't think speed is of essence here, as even a cruise (or in the case I'm proposing, glide) speed of say, 100 kts would be, knowing the infrastructure there , at least ten times faster.
I see one real problem though: landing at destination, automatic or remotely controlled? If rc, how? Satellite would be the only aplicable solution, but might prove troublesome with videostream bandwidth, lag etc. If automatic, oh man the effort of programming relating to all that needs to be taken into account. So: is dropping the cargo by parachute out of the question?

Based on all of these answers I posted a new more specific question. Yes parachute is the way to go as I see it.

@AidenKashi The MG-on-roids -concept combined with cargo drop with parachute would be quite feasible. Return trip would consume a fraction of fuel compared to the flight to target. Drop could be fully automated and dep - dest aerodrome being the same would enable rc t/o and ldg.

2000 miles with a piston engine has been done more recently - check Wikipedia's entry for the AAI Aerosonde, which crossed the Atlantic (2031 miles) burning only 1.5 US gallons of fuel. It includes a reference to the later "Spirit of Butts' Farm" which did that as well with a total gross weight of 11 pounds / 5 kilograms.
Autopilots are far more capable and small than they were then and often include autoland capability. What you want to do can be done.

The main distance limitation for a plane is weight: every extra pound of fuel means one less pound of payload. Planes can be equipped with "ferry tanks" that increase endurance for long open water legs, but then they're bumping up against (or even over) maximum gross weight with just the pilot (no passengers or cargo). Take the pilot out and you can add more fuel to go even further. Unless your goal is moving the plane itself, though, having no weight left for payload doesn't really allow anything useful to be accomplished.
Note that aircraft range is often specified for something like 75% power at cruise. Since drag is proportional to speed squared, flying slower would use a lot less fuel and thus extend your range, which may be fine for a drone that lacks the human need to stop every few hours.


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Can I make an emergency landing in Area 51?
In an emergency situation, it is permitted to land the aircraft anywhere. But does that include military bases such as Area 51? If my plane crashes and I determine that the safest place to land is Area 51, can I land there?

Just as a practical matter, when you're skirting the restricted area (which isn't just "Area 51"), there are lots of better landing sites outside, such as dry lakes, roads with generally very little traffic, and even a few actual airports.  To get to a decent landing place within the area, you generally have to fly over some rugged mountains.

@james What if there is a problem with the controls on the plane as it happened on United 232 and I end up inside the restricted area of Area 51?

@JeanExtreme002 You will meet with an unfortunate accident that the NTSB/FAA will be unable to corroborate the story of.

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Why isn't landing in the water a good option in an emergency?
Some people say that landing on water should be considered as a last resort because it is dangerous. But why exactly is it dangerous to land an airplane in the water? Wouldn't it be safer since theoretically, water would reduce the impact?
Note: I am referring to all planes (small and large).

Comments are not for extended discussion; this conversation has been moved to chat.

For one you can not "land on water" you can ditch an aircraft in a body of water but you would be hard pressed to call it a landing. You can however, "land in a grass field" or "land on a runway nearby" or "land on a highway" all of which are substantially more controllable then trying to stall a few feet above the ocean.
The result of catching an edge which can dig into the water is the same or worse than belly landing on grass. As others have mentioned at those speeds water is not so forgiving. but historically it tends to end poorly. While the miracle on the Hudson ended well Ethiopian Airlines Flight 961 did not have the same luck. You can see the outcome of contacting asymmetrically is pretty devastating.
The secondary concern is that even in a successful ditching still puts you in a sinking airplane with potentially injured people making rescue all that much harder.
Although Aviation Saftey Magazine paints an interesting counter point.

The Ethiopian Airlines case is not really a fair example.  I dare say it would be difficult to do a controlled landing on a runway while trying to fight off a hijacker.  As for landing on a grass field or highway, flat fields are hard to find in many parts of the country, while highways often have vehicles on them.

Missed the opportunity to joke about "can't land on water because you need to land on land... And you can't 'water' on water". Good answer, though =)

@jamesqf Also it seems lot of people survived from that crash ..

Because in most cases landing in the water is no different from landing on concrete. In fact, it could be much worse.
I'm not going to talk about the technicalities and physics behind it, but there are loads of reasons why you shouldn't land a plane in the water.
For example, the waves are a big threat.. Pilots usually try to land parallel to the waves, so the aircraft isn't pushed around and endangered. In the scenario that there are waves directly moving towards the aircraft, it's like running into a wall that's moving towards you.
And the most worst case scenario comes to the aircraft breaking apart. If an aircraft breaks apart upon landing, it greatly endangers the passengers and crew as the aircraft will begin to flood with water and sink.
All in all, when landing in the water, there are a lot of extra variables that pilots must deal with the execute a safe landing. So if you were given a choice of either landing on water or land, try landing on land first. Landing on water is always a last resort.

A simple answer is because you're less likely to drown on land. Open sea normally has waves of at least a meter, so any landing will be a controlled crash with structural damage. Part of the fuselage may be full of water very quickly, and there will be limited time to evacuate everyone, including the injured.
Once you're in a life-raft, exposure and hypothermia can kill in a few hours, and dehydration in a few days - and it can take that long for help to arrive. 10-20mph is common for ships, even a fast warship might only do 30mph, and you could be hundreds of miles from help. And that's assuming that the location beacons work, and bad weather doesn't prevent rescuers from spotting you.

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Helicopter or Airplane, which is the most difficult to fly?
I know it varies from aircraft to aircraft, but I want to know in general, which would be the most difficult aircraft to fly even after years of experience. Helicopter or Airplane ?
I tried to fly a helicopter on the FSX and I couldn't land the aircraft once without spinning like a beyblade for minutes. I know it is not possible to fly something perfectly without knowledge, but I remember that my first time flying a plane on the FSX, everything had been easier.
Some people also say that the wind greatly influences the helicopter on landing, which makes me think that perhaps the helicopter is more difficult to fly.

Helicopter.  I say... helicopter.

While this is an opinion-based question since difficulty is subjective, if you were to take a survey of pilots who have learned to fly both I think it would be very heavily skewed toward rotary wings being more difficult to learn. Perhaps once you're proficient in both they're more equivocal.

FSX has very simplified helicopter physics and it's not as realistic as Aerofly, X-Plane or DCS.

And even simplifying, it was more difficult (almost impossible) to land a helicopter than an airplane.

Unfortunately, this is an opinion based question. My opinion is based on the fact that my first few hours of helicopter instruction were harder than my first few hours of fixed wing instruction.
Takeoff in a helicopter was fairly easy after hover taxiing to the takeoff pad and hover turning 360° with yaw control to visually clear the area. Landing in a helicopter was fairly easy up to the point of bringing the aircraft to a hover. In both cases, the hard part came in the form of any of the low speed maneuvering. That includes just getting the skids off the ground and putting them back down under control.
Takeoff in a fixed wing aircraft was easy except for directional control to remain on centerline before rotation and the extended centerline after rotation. Landings in a fixed wing aircraft are in another realm of difficulty until you get the hang of it. From stabilizing the approach to slowing down to a speed appropriate to turn off the active runway and everything in between are hair-raising and nerve-wracking your first few hours of instruction.
Cruise flight in both is fairly simple and enjoyable once the aircraft is trimmed out and the friction locks are set properly. Although, changing flight parameters in a fixed wing can be done with as little as input on one control. Say for instance, changing the throttle input in a trimmed out airplane will make you change altitude. Changing flight parameters in a helicopter will involve input into more than one if not all of the controls. Changing the collective will require a change in throttle input, which will require input into the anti-torque pedals, in order to change altitude in a helicopter without a governor at low speeds.
The biggest difference is that a good instructor can verbally walk you through flying an airplane up until short final on your first flight. Although, they will always be ready and prepared to take the controls at any time. In a helicopter, the instructor will be on the controls the entire time your first flight. They will give you command of each control, one by one, as your confidence and competence grows.
Bottom line is that hovering is the deciding factor on whether it is harder to fly either a fixed wing or a rotary wing aircraft. Although, it is easier in a fixed wing. In a fixed wing aircraft, all you need is plenty of altitude, and a headwind that matches your airspeed (or an aerobatic plane with lots of thrust). In a helicopter, you need to be able to juggle while riding a unicycle.


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What is the VAC indication?
I pilot the plane cessna in the simulator for a long time, and I always saw this VAC indication next to the Ammeter. What is VAC for and how to read it?

Air pressure? I don't know dude.

In short, it is the vacuum gauge. It measures the vacuum pressure in Inches of Mercury. It runs/powers your non-electrical gyroscopic instruments. Those are your Attitude Indicator, your Directional Gyroscope, and sometimes your Turn Coordinator. These are all necessary to fly by Instrument Flight Rules.
Read these:
PHAK
Airplane Flying Handbook

That is, it is the basis for all instruments that use air pressure to work. But how to read this instrument? For example, if the indication is 4 or 6, what does it mean?

@JeanExtreme002 it means 4 or 6 "Inches of Murcury" - which is a/the unit of measurement for "pressure". The guage would indicate 4.5-5.5 is the correct range (based on the green arc)

@JeanExtreme002 - In general, your engine gauges will have an operating range indicated by colored markings on the gauge. This is to facilitate rapid acquisition of the required data. If the gauge is in the green, you are good. If it is not in the green, things are going to get rather sporty quickly. The above indication pictured would indicate that you have little to no vacuum pressure. Therefore, your Attitude Indicator and Directional Gyro will not work.

Is the "suction" indicator on some planes the same as the VAC?

Yes, in some planes it is.

It would behoove you to read the FAA manuals I have attached. They explain many of the questions you may have. If something is unclear after reading these, come back and ask questions regarding that specific section of the books. It will make your simming more effective and make more sense.

Ok, thank you <3


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Can a PP pilot fly large planes?
Assuming I'm rich, take a PP course and buy a Boeing 737 or A320. Could I fly these planes for non-commercial purposes?

In the US, yes. There are no restrictions from the FAA on the size of aircraft you fly with a private pilot certificate. If the aircraft requires a type rating, you would have to get that added to your certificate along with the category and class. The insurance carrier covering that aircraft would probably have much more stringent requires over and above the FAA requirements.
John Travolta has/had a Boeing 707 (similar to a B737) that he flies out of his private home/airport.

§61.31 Type rating requirements, additional training, and authorization requirements.
(a) Type ratings required. A person who acts as a pilot in command of any of the following aircraft must hold a type rating for that aircraft:
(1) Large aircraft (except lighter-than-air).
(2) Turbojet-powered airplanes.
(3) Other aircraft specified by the Administrator through aircraft type certificate procedures.
(b) Authorization in lieu of a type rating. A person may be authorized to operate without a type rating for up to 60 days an aircraft requiring a type rating, provided—
(1) The Administrator has authorized the flight or series of flights;
(2) The Administrator has determined that an equivalent level of safety can be achieved through the operating limitations on the authorization;
(3) The person shows that compliance with paragraph (a) of this section is impracticable for the flight or series of flights; and
(4) The flight—
(i) Involves only a ferry flight, training flight, test flight, or practical test for a pilot certificate or rating;
(ii) Is within the United States;
(iii) Does not involve operations for compensation or hire unless the compensation or hire involves payment for the use of the aircraft for training or taking a practical test; and
(iv) Involves only the carriage of flight crewmembers considered essential for the flight.
(5) If the flight or series of flights cannot be accomplished within the time limit of the authorization, the Administrator may authorize an additional period of up to 60 days to accomplish the flight or series of flights.
(c) Aircraft category, class, and type ratings: Limitations on the carriage of persons, or operating for compensation or hire. Unless a person holds a category, class, and type rating (if a class and type rating is required) that applies to the aircraft, that person may not act as pilot in command of an aircraft that is carrying another person, or is operated for compensation or hire. That person also may not act as pilot in command of that aircraft for compensation or hire.
(d) Aircraft category, class, and type ratings: Limitations on operating an aircraft as the pilot in command. To serve as the pilot in command of an aircraft, a person must—
(1) Hold the appropriate category, class, and type rating (if a class or type rating is required) for the aircraft to be flown; or
(2) Have received training required by this part that is appropriate to the pilot certification level, aircraft category, class, and type rating (if a class or type rating is required) for the aircraft to be flown, and have received an endorsement for solo flight in that aircraft from an authorized instructor.

Glad I could help.

It should be noted that all type rating check rides are to ATP standards, so while one might not meet some of the qualifications to actually get an ATPL or CPL, the bar is much higher than a PPL implies.

Yes, but with major caveats.

You'll have to get a multi-engine private rating.

You'll probably have to be instrument rated.

You'll have to get type-rated for the specific jet that you want to fly, and many type-ratings have fairly significant prerequisites

Most aircraft like that are not certified for single pilot operation, so you will have to get an appropriately type-rated co-pilot to fly it with you.

The costs and insurance requirements would be astronomical

But yes... its possible. John Travolta flew his own private 707 with a Qantas paint job.


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What are the CONT and FLT modes of the 737 start switches?
I pilot the PMDG 737 in my simulator and I know that before takeoff and before landing, the start switches must be set to CONT mode and at high altitudes in FLT mode. But what exactly are CONT and FLT mode? What they do ?

You really shouldn't accept an answer quite that quickly - it's generally recommended to wait a couple days for Stackers in other time zones to have a chance to respond.

Oh ok. This is a craze that I have come from other platforms, sorry.

No worries.  :-)  And now you know!

The 737 has two separate engine-igniter systems (each of which has igniters on both engines).  Each engine has four possible igniter modes (except for earlier-model Originals, which have five) - in clockwise order 'round the knob, they're GND, OFF, CONT (or, for early Originals, L IGN and R IGN), and FLT.

CONT mode turns one of the igniter systems on (which igniter system is used depends on the position of a separate switch), and is used for takeoff and landing.

GND mode on an Original or Classic, or on an NG that's on the ground, also uses a single igniter system, and is used for ground-starting the engines.

FLT mode turns both igniter systems on, the better to help keep the engines operating under adverse conditions, or maximise the chance of a successful midair relight.  In the real world, FLT mode is used only in conditions posing a significant risk of engine flameout (for instance, extreme turbulence or very heavy rain), or if a flameout has already occurred and one or both engines need to be restarted in flight - not for high-altitude cruise flight in general.

On an NG, GND mode is another option for inflight restarts, in which case it uses both igniters (unlike how it operates for ground starts).

Your simulator might be confusing FLT mode with OFF mode (neither igniter system operating), which is the setting normally used in flight (as combustion in a gas-turbine engine is generally self-sustaining unless the engine, or its fuel or air supply, is severely abused).

Additionally, on an NG, the EECs can automatically switch both igniter systems on (if an engine flames out) or off (if bad things happen during ground-starting), no matter what the position of the ignition knobs.

@JeanExtreme002, please either create a new question, or edit the question to cover all modes. Diverging discussion does not work well on this site as it orders posts by votes, not time.


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What is an aircraft magneto?
I know that magnetos are related to the engine and that on many planes, they are used to start the engine. But what exactly do they do in the engine?

They aren't used to start the engine.  Most GA engines have a conventional starter, which (like the alternator) is identical to ones used on automotive engines of that era.

He's an aircraft-themed supervillain, ably portrayed on screen by both Michael Flapsbender and Ian McKLM.

Did you make any attempt at all to research this question before posting it?

@PeterDuniho: More precisely, ignition magneto. But posting the question here is still useful even if there is information on Wikipedia

@Fred:  "posting the question here is still useful" -- frankly, that's debatable. But even if so, Stack Exchange users (even on aviation.stackexchange.com) are expected to do research before posting, and make sure that their question details what that research was, and what is specifically novel about the question that wasn't addressed adequately in their research.

There are some aircraft that use a generator-starter combo as one unit. This is an entirely separate piece of equipment from the magnetos.

A magneto is a gear driven electric generation device connected to the crankshaft of the engine. It supplies the ignition system (spark plugs) with power.
Each engine has two magnetos. Each cylinder has two plugs. Each magneto supplies one plug in each of the cylinders. This makes the ignition system redundant. If a magneto fails, the other magneto can sustain the engine.
Since the rest of the aircraft's electrical system is supplied by a belt driven alternator/generator, the engine is electrically isolated from any other electrical issues. If you lose electric power in the cockpit, your engine will still run. If you have to shut off electricity because of a cockpit fire, your engine will still run.
The scale of the image below is a little distorted. I had to get my phone pretty close to the oil filter for sufficient lighting.
MAGNETO #1 mounted below and to the side of the oil filter on the back of the engine

STARTER mounted under the front of the engine, connected to the flywheel only when in use

ALTERNATOR mounted under the front of the engine, connected via an accessory belt to the crankshaft

A mag is in effect a completely self-contained old-style generator/points/coil/distributor ignition system all crammed into a housing the size of two blocks of butter.
The drive off the engine accessory case spins an internal permanent magnet a/c generator, which energizes the primary windings of a built-in ignition coil, whose electromagnetic field is interrupted and caused to collapse at a specific sweet spot in the a/c voltage curve by the built-in breaker points, causing a voltage surge in the secondary windings of the built in coil, which goes out a built-in distributor to the plugs.
Take the points/coil system from a 1960s car, eliminate the battery and just include the car's generator, and you have what is in effect a magneto blown apart and spread around under the hood (although not exactly; the mag makes its power with an internal a/c current, not a dc current).
Because the power comes from an internal permanent magnet generator, they don't make much spark until spinning at a couple hundred RPM, so they need to be helped during start by a clock spring wind-up device, an impulse coupling, in the drive that temporarily stops rotation into the mag and stores the movement in the clock spring, then lets it go suddenly so the drive going into the mag spins really fast for a split second.  That's the CLICK you hear when you turn the engine by hand.  The mag can't make enough energy to get a decent spark at cranking speeds so starting an engine without an impulse can be tough.  The impulse coupler uses a centrifugal flyweight dog clutch to disengage itself as soon as the engine starts to spin quickly at start.
Mags have a fixed timing setting as well (typically mid 20s deg TDC), too advanced for starting (if you do get a spark it can make the engine kick back), so the impulse function also retards the spark while it's doing its job.
You could put an impulse on both mags, but it isn't really necessary for starting and it's a failure mode, so they are almost always installed on the left mag only and if you have key ignition it only enables the left mag when at START.  You turn a mag off by grounding out the primary circuit with the ignition switch to prevent the field-collapse function from occurring.  It'll still send a small voltage to the plugs if you spin it but not enough to jump the plug gap.
You have two of them partly for redundancy, and partly because the cylinder diameter is so large on piston engines the flame front takes quite a while to get across, so it's a lot more efficient to light the flame from two sides at once.

Is that 2 1-lb blocks of butter or 2 1/4-lb sticks of butter? :D

It's 2 of the blocks I get at Costco, whatever the heck they are lol.

Actual measurements would be more useful.

It’s about almost the size of an oil filter. I edited my answer to post a picture from a Piper Aztec engine.

Do magnetos generate power the same way as alternators? I always assumed they were different because of the name, but you make it sound like they're basically the same thing connected differently.

Magnetos use a permanent magnet to generate their electrical field. Alternators generally use electromagnets to generate their electrical field. Therefore, an alternator needs a small amount of electricity supplied externally to start generating more electricity. Magnetos do not. That is why a manual transmission car can be so hard to push start if the battery is completely drained or removed. Where as an aircraft can be accidentally started just by moving the prop. That is also why you have to disconnect/ground the mags on a parked plane.

Also, alternators produce AC (Alternating Current) electricity. This has to be converted to DC (Direct Current). Magnetos generally produce DC electricity.

The additional information is a lot more interesting that the Wikipedia article on magnetos. I'm glad this question didn't get deleted.

@T.J.L. well the Bendix mags on my O-290 are about 3" x 4" x 6", roughly.  Most mags on GA airplanes are Bendix or Slick.  Bendix mags are a lot more robust and last longer.  There is a recommended 500hr inspection on mags and if you send your Bendix ones in, it usually just gets new points/condenser, maybe new distributor and a couple gears.  With Slicks, most shops don't bother testing, they just overhaul them.

@DeanF.  I should have added "permanent magnet" to the text and have edited the post in response to your comment.  Thanks.

@JohnK - No problem. I should have added in my comment that I was responding to Skyler’s question/comment about the difference between an alternator and a magneto.

A generator produces power continuously as a magnet is moved toward or away from a coil.  A magneto stores up energy as a magnet is moved from a coil, and then releases it all when a contact opens.  While some energy will dissipate before the contact opens, and the amount of dissipation will be greater at slow speeds, a magneto need not be moving very fast to produce 50-75% of its normal voltage.

It's an AC generator with rotating magnets that continuously produce an AC current in the coil core where the primary windings are.  Being AC, there is a voltage being induced in the secondary windings, even with the mag off, and the flux field builds and declines during the polarity reversals.  The voltage isn't enough to jump a gap.  All the points do is trigger a sudden collapse at a sweet spot in the voltage curve instead of a gradual one.  Yes they don't need to spin that fast to make a decent spark so the impulse is only necessary at starting rpm.

For a more in-depth look at "left mag only" see https://aviation.stackexchange.com/q/80868/19656 .

You know, in a gasoline engine, we're putting gasoline and air into a cylinder in the engine, and then stuff happens, and plane goes zoom.
Well, the gas and air won't light itself on fire; it must be lit by something, and at a very specific time.
So, it uses a spark of electricity, in a "spark plug".
This shot of electricity is made the old fashioned way, by waving a magnet across a coil of wire. The coil of wire is designed by experts to do the right thing.   It's a common magnet, though a pretty strong one.
How do they get the timing right?  They put the magnet on a moving part of the engine, so it sweeps the coil at the right time.
Cars do this in a much more complicated way, with sensors feeding a computer which drives electronics and transformers. This is more reliable overall, but gives no warning of failure.
The airplane magneto would fail sooner, except they are overhauled at regular intervals, and that lets them see trouble coming. Still, many airplanes use two of them.

There are four basic types of gasoline ignition systems - magneto ignition (generator/coil all together in one unit), "standard" ignition (coil and distributor, with points & condenser in the distributor), "electronic standard" ignition where a Hall-effect transistor replaces the points, and modern electronic ignition with coil-packs on each cylinder plus crank and camshaft sensors which feed info to a computer which tells the coil-packs when to fire. Of them all the magneto system is arguably the most reliable, but is not the best performing. It's used in aircraft because reliability counts.

a magneto is a coil that reacts to a magnet fitted on the shaft in order to generate electricity for the spark plugs alone. is already set and timed for spark. it is redundant for this reason and independent of the alternator that generates auxiliary electrical power. is a vital component meant to still maintain spark power for emergency situations, but not meant to provide electrical power for any electrical auxiliary.
you may find magneto also on the boat engine, because of its inherent simplicity and reliability.

authors: Bob Jarvis - Слава Україні


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What is this instrument above the EGT in the Boeing 737?
I would like to know what is this instrument that is above the EGT of the Boeing 737. What does it indicate?

(What's an altitude horn?)

@BruceWayne (Your favorite search engine knows the answer.)

@BruceWayne You should ask that as a question.

Chemtrail tank indicator

The face of the "EGT" gauge is in the wrong spot... that's not where it belongs.

This is a differential pressure and cabin altitude indicator.
The outer dial indicates the difference in pressure between the inside of the cabin and the outside in psi. During takeoff and landing, it must not be larger than 0.125 psi, as the note below the instrument says. If it exceeds 9.1 psi, the pressure relief valve will release the pressure to prevent damage to the airframe:

Two pressure relief valves provide safety pressure relief by limiting the
  differential pressure to a maximum of 9.1 psi. A negative relief valve prevents
  external atmospheric pressure from exceeding internal cabin pressure.

(Boeing 737 NG FCOMv2 2 - Air Systems - Pressure Relief Valves)
The inner dial shows the cabin altitude in thousands of feet. During normal operations, it should not exceed 8,000 ft. This is a measure of the absolute pressure inside the cabin, converted to an altitude using the standard atmosphere (ISA) pressure profile.
Note: The instrument below is typically a cabin climb indicator showing the rate of change of cabin altitude in thousands of feet per minute:

(image cropped from here)
The EGT instrument in your image shows the Exhaust Gas Temperature of the APU and is typically installed further to the left on the overhead panel.

As per this article, it's a Cabin & Differential pressure gauge (Boeing).
Here's an explanation:

The differential pressure gauge shows the difference between the pressure inside the aircraft and the pressure outside. So you would expect that diff pressure would be zero when you are on the ground and the passengers are boarding. When you are climbing, in cruise and arriving, the diff pressure shuold be positive; basically it should increase as you climb since the pressure outside decreases but the pressure inside remains the same (it decreases as well but not as much as the outside). On final you should again have the zero diff pressure.

(source)


text:
Transonic Airfoil with high critical mach number
does anyone know, how I can find a transonic airfoil (high subsonic, Ma=0.88) with a high critical mach number?
I know that if I know c,0,min = minimal pressure coefficient of the airfoil, then I can calculate the critical mach number.
But when I use Xfoil for plotting the pressure distribution, I only get a nice picture, but I can not write out the data for the pressure distribution. otherwise I could determine the critical mach number.
Maybe someone has some hints for me?
Thank you
Lucas

If you enter the flow conditions correctly, XFOIL will plot a dashed line at the critical c$_p$.

First I have to say that XFOIL is not the right tool for such a high Mach number. Professor Drela has written ISES to address the shortcomings of XFOIL at transsonic speed.
Next, the critical Mach number is well defined as $$c_{p_{crit}} = \frac{2}{\gamma\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{2}{\gamma+1} + \frac{\gamma-1}{\gamma+1}\cdot Ma_{\infty}^2\right)^{\frac{\gamma}{\gamma-1}}-1\right)$$
which can be simplified for air as $$c_{p_{crit}} \approx \frac{1}{0.7\cdot Ma_{\infty}^2}\cdot\left(\left(\frac{5+Ma_{\infty}^2}{6}\right)^{3.5}-1\right)$$
$\gamma$ is the ratio of specific heats and is 1.405 for air.
For $Ma_{\infty}$ = 0.88 this is -0.23 which is too little to even accommodate a moderately thick airfoil without supersonic flow. Therefore, your wing needs sweep to function well. Even then, I recommend a supercritical airfoil which will have supersonic areas at this speed but without a big drag penalty. Take your pick.

It sounds like you're looking for a Supercritical section, so this NASA report on Supercritical Airfoils may be of use.


text:
How do you calculate Profile Drag?
second year aeronautical engineering student here. I'm doing some aerodynamics coursework but have run into a problem.
I've read through the answers to the question "what is profile drag?" but nowhere either there or elsewhere online can I find how to calculate the profile drag. I can get the skin friction drag from boundary layer calculations, but have no idea where to go from there. So does anybody know how to calculate the form drag for a given aerofoil (eg NACA4412)?

I'm not sure you can. Maybe it's just what's left when you've subtracted the calculated values for skin friction and induced drag? These are all just mathematical abstractions for complex systems.


text:
How do I maximize flight hour usage in getting an instrument rating?
I recently finished a private pilot certificate and I'd like to get a instrument rating while keeping my costs low.  I understand I'll need 50 hours of cross country PIC time (VFR) and 40 hours instrument training.
Question:  If I fly under the hood with a Safety Pilot on cross country flights for 15 hours, do those 15 hours count both towards the 50 hours of cross country PIC time and towards the 40 hours of instrument training time?
Here is the breakdown of what I think I would need:
50 hours cross country PIC time consisting of:
15 hours cross country PIC time I already have,
15 hours cross country PIC time while under the hood with a Safety Pilot, and 20 hours cross country PIC time solo (or with a friend).
40 hours instrument training, consisting of:
4 hours already completed with instructor (3 from PPL),
15 hours under hood with Safety Pilot,
10 hours with instructor in Redbird simulator,
and 11 hours with instructor in airplane.
Am I getting this right?

Closely related

Thanks, but this doesn't quite answer my question about overlap of the 15 hours under the hood with a Safety Pilot - do those 15 hours count both towards the 50 hours of cross country PIC time and for the 40 hours of instrument training time?

I don't want to sound unhelpful but you might want to review the requirements in 61.56(d), assuming you want an airplane IR. You seem to have a couple of misunderstandings, e.g. the 40hrs is instrument time, not instruction time. If you don't understand the requirements then of course feel free to ask about them here, preferably by quoting the part you didn't get. I think that will help to make your question clearer, and to get you a better response.

I'm just wanting to know if I can double dip on hours - if I can count hood time with a Safety Pilot both for the 50 hours of cross country PIC time and for the 40 hours of instrument time.

That's helpful, thanks! Although I believe that's already answered in your other recent question about using a safety pilot while logging time cross-country time.

OK, so the answer is yes.  I thought so, but I was just making sure.  That reduces the cost quite a bit.

@Pondlife either make your comment an answer, or we need to close this as a dupe.


text:
Reporting an ambiguous driving record case on my medical application
I am filling out my renewal application for a third-class medical.  It asks about my driving record, and about 15 years ago I was living in California with a valid driver license from another state and using that to drive, and since I had lived in California for more than 30 days without getting a California license, I was going to be accused of driving without a license (after a traffic stop for an expired registration).  I got a letter from the district attorney saying that since I was a first-time offender I could do a "character improvement program" which was a workbook that some company mailed to me, and I did the workbook and paid the $300 fee and that was the end of it.  I am looking at my California driving record and I do not see anything at all about that on my driving record.  Do I need to report this on my medical application, even if there is no mention of it on my driving record?  Another thing is that I forgot to report it on my last application, and apparently my driving record was good enough because they issued me a medical certificate.  If I mention it this time, they may wonder why I didn't report it last time.

You should talk to AOPA's pilot protection group.

Yeah, that's probably the thing to do.  Thanks.

I honestly don't recall seeing any questions about driving records on a medical application.  (and I have had 2nd and 1st class medicals)  Is this really a thing with the FAA?  In any case, it is an administrative issue, not a moving violation like a DUI.  It is about as applicable to your medical health for flying as paying your phone bill 3 days late is relevant to a doctor's clearance to play sports.


text:
Can I fly a practice LNAV approach with an iPad?
I'm doing training for an instrument rating, and I'm thinking I'd like to do some solo VFR cross country flying and do some practice instrument approaches.  The C152 I'll be flying doesn't have a GPS installed, but I'll have ForeFlight on my iPad.  Since I'm VFR, could I request a practice LNAV approach from ATC and use my iPad to navigate the approach?  I realize this isn't quite as good as doing hood training in an aircraft with GPS, but I think it will be of some use to me in my training.

This question is specific to flying an LNAV approach, not navigating generally. Other than "you're VFR, do whatever," not much from that question addresses this one specifically. Voting to leave open & not a dupe.

In the US, there are no regulations prohibiting you from using an iPad for navigation while flying VFR. There are also no regulations specifying what equipment you must use for a practice approach. The key to this is that it is a practice approach. Therefore, it is flown VFR. Even if you were an IFR-rated pilot in an IFR aircraft under the hood/foggles, your safety pilot would be VFR.
If you fly that same approach IFR (whether IMC or VMC), then it is an actual approach even when done as a practice approach. Just the ATC expectations are changed. Flying IFR would require the proper TSOed navigational equipment.
One word of caution would be that this might not be a safe practice flying solo. It would be best to have your iPad mounted somehow to make it hands-free. You should also practice this with your CFI (preferably) or a safety pilot first.
It would also be unwise to have to switch back and forth from the approach chart to your Foreflight  AHRS screen on the same iPad. You are in a critical phase of flight. Doing what you plan would be an unnecessary distraction and a violation of the Part 91 sterile cockpit strong recommendation (not a regulation for Part 91, yet). Either print your approach charts or carry two iPads.
Some guidance for practice approaches is provided in AIM 4-3-21.

I think this (and the answer below) are the right way of thinking about it.  There might be some benefit, but it won't be quite the same practice as doing an approach under the hood with the right equipment.  And flying VFR means that I'm responsible to see and avoid, which will be more difficult if I'm looking at the iPad and switching back and forth on the screen.  So maybe I'd be better off to do a real practice approach with a safety pilot, which would also be cheaper because we'd split the cost.

One other thing I would add to this is you aren't following a CDI which on an LNAV approach provides your lateral guidance from GPS. The CDI scales down for approaches so it's more sensitive. Following the iPad doesn't give you this. So while perfectly legal VFR, I don't really see a lot of training value in this, since it really doesn't simulate doing an actual IFR approach other than stepping down in altitude at each fix which you can do anywhere you want VFR.

Yes, you can do this.  As Ralph J says, "You're VFR, do whatever".  That said, you should understand what you are getting and not getting from this practice.
On the Plus side:

You are practicing interaction with ATC
You are being introduced to a diverse set of procedures

On the Minus side:

You are practicing use of navigation which is illegal under IFR.
You are getting neither simulated, nor actual IMC time in your logbook unless certain conditions are met.

I'd say, go for it with while understanding the benefits and limitations of what you are doing.

I do it all the time. You can fly VFR with any device or no device.
A couple of things that I’ve noticed. If you request a VFR practice approach and they approve it, they’ll fit you into the traffic flow just like IFR traffic. They may give you vectors to fit faster traffic into the flow—which is great practice.
If you just fly the RNAV and don’t tell them what you are doing, they sometimes give me 360° turns for faster or slower traffic. But they don’t know that I’m trying to track the approach so they are doing whatever it takes to keep traffic flowing.
I usually inform ATC of my intent when I’m a couple of miles from the IAF so they have time to clear me for the approach. Again, if you don’t tell them you want an approach they may just assume you are headed for the airport and hand you off to the tower where you might get told to fly a base or downwind entry.
As long as you communicate your intentions and use the magic words, “Remain VFR” it works fine.


text:
Do WINGS activities count when your medical is expired?
I flew with a flight instructor a few months ago, and he gave me a WINGS credit for the flight.  My medical was expired at the time.  I have since renewed my medical and it's current now, and I'm going to do more flights to get two more WINGS credits to count as a flight review.  The WINGS programs states that pilots must have a medical certificate to participate in the program.  Do I have to do that one WINGS activity over again since my medical was expired at the time I did it?  I have already been given credit for it on the WINGS website.

From AC 61-91J (emphasis mine):

All pilots (including student pilots) holding an FAA-issued pilot
certificate and any required medical certificate may participate in the WINGS Program.

It doesn't say "any medical certificate," it says "any required medical certificate." My reading of this is that certain tasks require a medical certificate, and you can't participate in those tasks without one. For instance, you would need a medical certificate for a task that requires soloing but not one that involves receiving dual training or going to a seminar.
The FAQ reinforces this, with more clear wording: (emphasis mine)

Q. Who can participate in WINGS?
All pilots holding a U.S. pilot certificate and a current medical certificate, when required, including student pilots, may participate in the WINGS Program and receive a flight review date extension upon completion of a Phase. However, we encourage participation even if you don't hold a current certificate. Retired, foreign and student pilots can still benefit from the safety training offered on nFAASafety.gov and through the WINGS program; however the flight review date extension you may receive by completing a Phase of WINGS will not be valid without a current certificate.

Ah yes, this sounds right.  So the previous activity does count.  Thanks!


text:
Do I have to re-report old conditions on each medical renewal?
When I first filled out the application for an FAA third-class medical it asked "Have you ever in your life had these conditions?"  I put yes for a few of them, had some tests done, and was issued a standard medical.  So now I am going in for a renewal and it asks me the same question of "Have you ever in your life had these conditions?" Do I need to re-report the old conditions, even if I have not had any new symptoms?  I mean, if you had some medical condition that happened in the past and is now is gone, and you've been approved for a medical certificate, do you have to keep re-reporting that same past condition on every medical certificate renewal for the rest of your life, even if you have no symptoms?

Yes, you must always report these conditions on Form 8500-8, forever. But you can write "PREVIOUSLY REPORTED, NO CHANGE" in the EXPLANATIONS box as explained in the form's instructions (emphasis mine):

18. MEDICAL HISTORY - Each item under this heading must be checked either "yes" or "no." You must answer "yes" for every condition you have ever been diagnosed with, had, or presently have and describe the condition and approximate date in the EXPLANATIONS block.
If information has been reported on a previous application for airman medical certificate and there has been no change in your condition, you may note "PREVIOUSLY REPORTED, NO CHANGE" in the EXPLANATIONS box, but you must still check "yes" to the condition. Do not report occasional common illnesses such as colds or sore throats.

I'd also suggest you keep the records of any extra tests previously done. If your medical examiner wants to investigate any of the conditions, the old test results may be enough to satisfy them.

You can even shorten that up to writing "PRNC". I've been doing that for decades. Never had an AME even bat an eye.


text:
Am I Required to Use the Runway Advised by a Unicom?
Let's say that an uncontrolled airport's ASOS reports wind 060 @ 6 knots.  The airport's unicom advisory states that Runway 22 is in use.  Am I required to use Runway 22, or can I use Runway 4?

Closely related, perhaps a dupe?

At uncontrolled airports landing is entirely at the pilots discretion, that includes which runway you use. Advisories are just that, the decision is up to you unless a runway is actually closed.
Listen out on the CTAF and listen to what the other pilots are doing, if they are using 4 then use 4 too, if they are all using 22 then there is probably a reason for it.

You are not required, but it is advisable if there are other aircraft in the pattern.  My home airport often does not have anyone in the pattern and pilots that are based there will sometimes land opposite of the advised runway because their hangars are located at the other end of the runway from the FBO.  This means that they can either land long or do a long rollout after landing and then turn off at their hangars.  If they landed on the advised runway, they would having to taxi all the way back down from the FBO end of the airport or applying brakes to try to make one of the turnoffs to the taxiway.  You just listen on the CTAF and announce your intentions if you don't hear anyone.  It is probably more used when a pilot is flying back and wants to just make a long straight in approach while also ending up at his hangar with minimal wait time.

As PIC, you are solely responsible for the safe operation of your aircraft. Unicom is an advisory service meant to assist you in that goal, but unlike ATC, you are free to ignore it.
I read about an incident where Unicom advised an inbound pilot that a particular runway was in use based on the last aircraft they'd heard on the radio. However, the winds had since shifted and there was a NORDO plane in the pattern for the opposite runway, which the Unicom operator wasn't aware of because they didn't actually have eyes on the field. I don't recall how it ended (comments welcome), but you can imagine how easily that could turn deadly.

As the other posters have said, you can use whatever runway you want, within reason. Uncontrolled really means pilot controlled. It is up to the pilot to determine the safest runway to accomplish his/her mission. If the winds are favoring a specific runway, it would be safer to land facing into the wind. If there are aircraft already in the pattern, it would be safer to keep your pattern consistent to theirs. If the mission for your flight is to practice crosswind or tailwind landings (just in case you have an engine out above your particular “impossible turn” altitude), take into account your personal minimums and go for it. Always communicate your intentions to your fellow pilots regardless of the runway you are using. And, an overhead flyover well above Traffic Pattern Altitude beforehand is recommended. Keep an eye out for anyone not communicating on their radios.


text:
Should I use rudder to recover from power-on stalls?
I was executing a power-on stall, and upon stalling the nose dropped and the plane rolled hard right.  I promptly applied left rudder and released yoke backpressure to recover, and the plane recovered normally.  However, my instructor told me that I should not use rudder when recovering from a power-on stall, even when the plane rolls one way or the the other.  This confused me, because a DPE had told me not to use ailerons when recovering from a power-on stall if the plane rolls one way or other other, so I'm not sure how I'm supposed to level the plane if I can't use either rudder or aileron.  Also, I had thought the roll was the beginning of a spin, but my instructor told me that it was not and that we were nowhere near a spin.  Can someone clarify the use of rudder (or aileron) on recovery from a power-on stall?  And if I'm in a situation where my plane is stalled and I'm rolling hard one direction, if that's not a spin, can someone please clarify what a spin is?

You were uncoordinated when you stalled, that's why it rolled, you need to be using the rudder in the approach to stall to stay coordinated. What aircraft are you flying?

I'm flying a Cessna 172.

It sounds like the beginning of a spin entry to me. You reacted the way I was taught. Using ailerons at slow speed can have the opposite effect. I suspect you were not balanced as Ron mentioned, as if you were the engine torque would tend to break to the left.

My suggestion right now is do as your instructor says. Next lesson Ask to get a demonstration or try for yourself.
The full answer is to follow the operations manual. Airplane types vary a lot. The 172 is a very benign type as far as they go. A bit of performance has been traded for simple and safe (well) handling. Other types can be quite nasty, given wrong control inputs they bite.

Interesting discussion on the topic here.
Most notably, the Australian aviation authority updated their guidance to add:

apply rudder to prevent the nose of the aeroplane yawing into the direction of the dropped wing

I believe this recognizes that there is a very short duration in the maneuver where coordinated rudder inputs are not possible yet, but where a spin can be prevented by stopping the yaw using rudder inputs. Almost immediately this is followed by:

ailerons should be held neutral until control is regained, when the wings should be levelled using coordinated inputs

Your instructor is correct.
I've never seen a C172 where the POH actually discusses stall recovery besides saying it's 'standard'. I was taught to keep the airplane in balance using rudder in the approach to the stall, and manage any wing drops with rudder in a fully developed power off stall (I'm in the UK, not sure how the US is different). However, that isn't the procedure for a power on stall. The FAA Airplane Handling Handbook section 4-8 on power on stalls states:

The pilot must promptly recognize when the stall has occurred and take
action to prevent a prolonged stalled condition. The pilot should
recover from the stall by immediately reducing the AOA and applying as
much nose-down control input as required to eliminate the stall
warning, level the wings with ailerons, coordinate with rudder, and
smoothly advance the power as needed. Since the throttle is already at
the climb power  setting,  this  step  may  simply  mean  confirming
the  proper power setting.

In a power on stall if you get a big wing drop the rudder is not going to lift the wing, and coarse rudder movements could stress the airplane, see the AA 587 crash. So balance with rudder, but most importantly reduce your angle of attack with as much forward stick as you need.

Rudder is not used for recovery but is an extremely valuable tool to control yaw while plane is being unstalled by reducing AOA.
Ailerons should not be used as a roll control reversal can happen if the lowered aileron causes its wing to stall, while the other wing (with the raised aileron) remained unstalled.
Reducing power also makes the situation less complicated by reducing P and engine torque effects. There will be schools of thought depending on the type of aircraft.  A very large or heavily loaded aircraft needs power and airspeed.  Push the yoke forward first if signs of stall develop.  Many times this is all that is needed.
Applying opposite rudder in an incipient spin (ok, its not fully developed yet but let's act now) is not a bad move as the control input to stop the spin is now already in.  With a dropped wing the plane will be in a side-slip. Not a major issue provided the plane is promptly unstalled by reducing AOA (with elevator).
Speaking of incipient spin, we also have the incipient stall: the buffet and stick shake.  There is also the stall warning horn.
Do not ignore these.  Be proactive and reduce AOA immediately, rather than falling further and further into trouble.


text:
Can instrument training be done in IMC with an instrument-rated safety pilot?
I'd like to fly some hours towards an instrument rating by flying with a safety pilot.  I have a safety pilot who is instrument-rated and current (he's working on building time towards a commercial rating).  Since he's instrument-rated, can we fly in IMC on an instrument flight plan?  If we do, can I be the manipulator of the controls, and can I log PIC time for the time that I'm the sole manipulator of the controls in IMC?  And if we're in IMC on a instrument flight plan, do I need to be under the hood by using a view-limiting device, or is just being in IMC good enough to count as instrument time?

If you are the sole manipulator of the controls then yes you can log PIC time in this scenario, however you cannot act as PIC. The FAA discusses this in at least two letters of interpretation Speranza 2009 and Walker 2011. Both which lay out effectively the same situation (I would advise reading them) but in short they go into the fact that acting as PIC is not the same as being the sole manipulator of the controls and thus logging time as PIC.
Interestingly the IFR Rated pilot cannot log the PIC time while you are the sole manipulator of the controls as there is no prevision for that in the safety pilot regulations. The FAA words it as follows:

However, Pilot A may not log PIC time for the portion of the flight during which Pilot B is the sole manipulator of the controls, and is logging PIC time, because there is no provision for this logging in 61.51(e)
...
Although Pilot B [non IFR Rate Pilot] properly may log PIC time for a
portion of the flight as discussed previously, Pilot B could not act
as PIC and was not a required flight crew member for any portion of
the flight under the aircraft's type certificate or the regulations
under which the flight was conducted.
Speranza 2009

If you are in IMC then you do not need a hood as you would log that as actual IMC
The Herman Interpretation (2009) may also be relevant reading r.e. logging PIC vs Being PIC

That's not clear, I think you are saying no but it's hard to interpret. My understanding is that if it would be illegal to be PIC in actual IMC without an IR.

@GdD the FAAs wording here is a bit vague but there is a difference between acting as PIC and logging PIC time. A non IR pilot could not accept a clearance but they could physically be in control of the airplane in IMC and log that time. The Herman interpretation 2009 explains this a bit more

So what I hear you saying is that if I were to fly in IMC with an instrument-rated safety pilot, I could log the time as both instrument training and PIC time, but my safety pilot would not be able to log any PIC time.  But this doesn't make sense to me because he must be PIC, as we're in IMC on an instrument flight plan and he's the only one with an instrument rating.  So in this scenario, he would be PIC but he would not be able to log PIC time; I would not be PIC but I would be able to log PIC time.  That doesn't seem right at all.

Update: so I read the Walker Letter and this pretty clearly answers the question.  In my scenario, I can log PIC time but the instrument-rated safety pilot can't.  That's good for me and bad for him, so that will probably be a no-go.  This seems like a silly hair-splitting exercise in government bureaucratic rule-making, but I guess it is what it is.

@SurfandSky In the letters they even admit there is no prevision in the safety pilot regulation to allow the "acting PIC" to log the time in IMC. This is the classic "double dip" question that comes up often for safety pilot scenarios and maybe the regulation should be updates. Call your senator and ask!

Your safety pilot not a CFI or CFII - therefore this is not instruction and can not be logged as such.


text:
Are there any cases where the back-seat pilot is the only one who can cause both ejections seats to fire?
In military training aircraft with a tandem seating configuration, with the instructor pilot in the back seat and the trainee pilot in the front seat, is the ejection system ever set up so that there is a mode where the back seat occupant can eject both pilots, but the front seat occupant can only eject himself/herself?

Related: https://aviation.stackexchange.com/q/23654/34686

Obviously, I can't answer with certainty about what might exist, but as far as I know, NO. This would make no sense, as once the pilot is gone, why would the rear seat occupent want to hang around?
In the F-4 Phantom, (USAF versions), there was a switch in the rear cockpit (called the Command Selector Valve), that controlled whether or not the front seat ejection sequence would be triggered when the rear cockpit occupant initiated an ejection.
But the rear cockpit ejection sequence was always triggered if the front seat occupant ejected.
Regardless of who initiated the ejection, the rear seat would be ejected and depart the aircraft first, followed by the front seat 2 seconds later. This was to avoid the front seat rocket motor from frying the rear seat occupant.

I'm not sure that this answer addresses the exact question being asked-- perhaps would be better posted as an answer here?  --  https://aviation.stackexchange.com/q/23654/34686

The specific answer was implied... thought that was obvious, but I edited it to state it explicitly.

re "This would make no sense, as once the pilot is gone, why would the rear seat occupant want to hang around?" --  in the present question, both seats are occupied by "pilots", but the one in front may be a inexnperienced trainee.

Which makes one tend to think of the situation that is addressed by the "Normal" mode described here https://aviation.stackexchange.com/a/93617/34686 -- except the position of the "experienced" crew member versus the "inexperienced" one is reversed.


text:
How do I fly to Borrego Valley (L08) if it's inside a CA state park?
I'd like to fly to Borrego Valley Airport (L08) and it's inside California's Anza-Borrego Desert State Park.  How does this work, given that I'm supposed to say at least 2000 feet AGL when flying over a state park?  Am I allowed to descend below 2000 feet AGL only for takeoff and landing at the airport, or can I be below 2000 feet AGL at other times when flying over the state park?

Related

You should minimize your time less than 2000 ft AGL while safely operating the aircraft to arrive at Borrego Valley (L08). I would interpret the rule to mean I will only descend below 2000 ft AGL when it is required for my safe descent to arrive at a normal pattern altitude in a safe position to land the aircraft.
Here's an excerpt from FAA Advisory Circular 91-36D titled VISUAL FLIGHT RULES (VFR) FLIGHT NEAR NOISE-SENSITIVE AREAS that explains this rule:

b. Pilots operating noise producing aircraft (fixed-wing, rotary-wing and hot air balloons) over noise sensitive areas should make every effort to fly not less than 2,000 feet above ground level (AGL), weather
  permitting. For the purpose of this AC, the ground level of noise-sensitive areas is defined to include the
  highest terrain within 2,000 feet AGL laterally of the route of flight, or the uppermost rim of a canyon or
  valley. The intent of the 2,000 feet AGL recommendation is to reduce potential interference with wildlife
  and complaints of noise disturbances caused by low flying aircraft over noise-sensitive areas.
c. Departure from or arrival to an airport, climb after take-off, and
  descent for landing should be made so as to avoid prolonged flight at
  low altitudes near noise-sensitive areas.
d. This advisory does not apply where it would conflict with Federal Aviation Regulations, air traffic control clearances or instructions, or where an altitude of less than 2,000 feet AGL is considered necessary by a pilot to operate safely.

Source: FAA Advisory Circular 91-36D, dated September 17, 2004

I agree. The 2000 foot request pertains to overflight of a wildlife area. I think that would be the least of my concerns. The MEF and the SUAs to me are bigger concerns. Considering that if it were flat land, I could stay at more than 2500 AGL up until 2 miles from the field. Then, forward slip it down to TPA for my 45 degree entry to downwind. Getting on flight following and staying on a prescribed charted procedure will help keep a pilot from running afoul any regulator issues.

Having never flown into this airport before, I would study the sectionals and charts very carefully. The state park is one concern. There are specific notes on the sectional requesting aircraft to stay above 2000 feet. There are also restricted areas, military training areas, laser illumination areas, etc. all around the airport. Not to mention the rising terrain and obstacles as high as 7100 feet around an airport with a 522-foot field elevation and a 10,000-foot Minimum Sector Altitude. Then, the airport having to have a specific obstacle departure procedure is a big red flag for me.
If it were me flying into this airport, I would request flight following to the RNAV (GPS) RWY 26 IAP all the way in to the traffic pattern. Then, I would land straight in or circle to runway 8. The minimums are probably a full 1200 feet above the field elevation for a reason. Remember to circle South of the airfield (right traffic pattern for runway 8). And, do not overfly the area Northwest of the field nor the elementary school 1 nautical mile West of the field. This is from a quick glance of the charts and chart supplement.

@RouteMapper - I agree. The 2000 foot request pertains to overflight of a wildlife area. I think that would be the least of my concerns. The MEF and the SUAs to me are bigger concerns considering that if it were flat land, I could stay at more than 2500 AGL up until 2 miles from the field. Then, forward slip it down to TPA for my 45 degree entry to downwind.

Also important to note the obstacle descriptions from the ZUNGU ONE departure procedure.
"Rwy 26: Numerous trees beginning 1000' from DER, on centerline, up to 75' AGL/875' MSL. Rwy 8: Numerous trees beginning 2000' from DER, 400' left of centerline, up to 75' AGL/634' MSL"

I think OP's question is specifically about the noise sensitive area, though. Everything you said is valid and helpful for planning to an unfamiliar field, though!

@RouteMapper - I think you are correct. And, your answer addressed that specific concern quite well. I don’t want the OP to not see the forest because of the trees. He should take a look at the bigger picture. He’s requested not to fly lower than a specific height nor over certain areas like the school. But, he is also given a legal corridor right into the airport of which he can take advantage while remaining safe(r).

The RNAV (GPS) RWY 26 IAP says "Circling not authorized south of Rwy 8-26". But the airport remarks say "ALL ACFT TFC PATS TO S.". Interesting.

@RouteMapper - Very interesting, indeed. The chart supplement also says that rwy8 is right traffic. And, there is aerobatic activity North up to 5000 feet. I guess that means that you will have to cancel your VFR practice approach at or before the MAP, sidestep wide South, and come into the right downwind at a 45 degree angle. I wonder if all read the same prior to the May 21st update.


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If the ATC controller switches me to a visual approach midway through, does that still count as an instrument approach?
I was flying my 250-mile "long cross country" for my instrument rating as outlined in 14 CFR 61.65(d)(A)-(C). I had done two instrument approaches at two other airports, and my third approach was an LDA approach into a large Class B airport. We were cleared for the LDA approach, and then halfway through the approach, the controller said to us, "Cleared for the visual approach." I assume the controller did this out of habit and to expedite the flow of traffic at a busy airport. Does that mean that my third instrument approach is null and void and no longer counts as an instrument approach because it was changed by the controller to a visual approach? Do I now have to redo the entire 250-mile cross country because the controller switched me over to a visual approach halfway through an instrument approach, and therefore the instrument approach doesn't count?

Not helpful for you now, but just to be aware, you always have the option to decline the clearance for a visual approach.  The controller may not be happy, and if his options are either your approach becomes a visual, or he breaks you off of the training approach, or he has to make somebody else go around, well... you may get the "cancel approach clearance, fly runway heading, climb and maintain..." response. But even having reported the runway in sight, you aren't required to accept clearance for a visual approach.

@RalphJ I guess if he's on the LOC on final and the controller clears him visual, there's nothing stopping him from accepting the clearance and flying the LDA profile anyway, but to the question, for the purposes of meeting the legal training requirement, does the visual clearance invalidate it as a training/experience exercise?  Probably it's useful to mention that the approach to be flown is to meet training requirements during the arrival.

@JohnK  Yeah, fair point. If you have an uncontrolled airport and the safety pilot or CFII provides "vectors" around the pattern to intercept the ILS, does that count for currency purposes, even if ATC never said the words "cleared ILS runway XX"?  I'd assume so, but that's not my world.  We can log our Cat III approaches in VMC regardless of what ATC cleared us for as long as the switches & procedures in the cockpit are done (and since it's HUD & not autoland, we don't have to have the safety area protected). Interested in an authoritative answer to this.


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Is the mach number of an aircraft measured with respect to stagnation speed of sound?
I was reading chapter 8 of JD Anderson Aerodynamics when I came across something I find weird. I found out that there are different types of Mach number, based on what the speed of sound was taken as. Now my question is this, when we say "That plane is flying at Mach 1", is it with respect to the stagnation speed of sound, ie, (approximately 330 m/s), or is it with respect to the actual speed of sound?

The Mach number is defined with respect to the static speed of sound.
Note however that the Mach number is not measured by somehow measuring the TAS (True AirSpeed) and dividing it by the known speed of sound because this would require knowing the static speed of sound, which is temperature dependent. Instead, we derive the Mach number from the ram air pressure $p_0$ measured by the pitot tube and the static air pressure $p$ measured by the static port:

$$ M^2 = \frac{2}{\gamma - 1} \left[ \left( \frac{p_0}{p} \right)^{(\gamma - 1) / \gamma} - 1 \right] $$
[...]
The velocity can be determined from
$$ V^2 = a^2 M^2 = \frac{a_0^2 M^2}{1 + \frac{\gamma - 1}{2} M^2} $$
but this requires knowing either the static speed of sound $a$, or the stagnation speed of sound $a_o$.

(MIT Lecture Notes on Subsonic Pitot Tubes)
You can see in the velocity equation that the Mach number $ M = V / a $ is defined via the static speed of sound $a$ instead of the stagnation speed of sound $a_0$.
The above equations are only valid for subsonic flow. If you want to determine the Mach number in supersonic flow, you have to solve the following equation iteratively:
$$ M \approx 0.88128485 \sqrt{\left( \frac{p_0}{p} + 1 \right) \left( 1 - \frac{1}{7 M^2} \right)^{2.5}} $$
(Wikipedia - Mach Number)

Thank you for the answer! I had another doubt in the same. We know the temperature changes with altitude, and in turn the speed of sound too, right? Now the temperature measured by say a thermometer at rest at an altitude at 10km, is that the static temperature or stagnation temperature? It must be stagnation cause it is at rest right? Or am I wrong?

Temperature changes with altitude and therefore also speed of sound $a \sim \sqrt{T}$. The temperature measured by the aircraft is called TAT (True Air Temperature), the probe is called a TAT Probe. The temperature measured at rest is usually called the SAT (Static Air Temperature) and cannot be measured directly (but calculated).


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What geographic reference system do airport towers use?
What geographic reference system (WGS84, EGM96, EGM2008 etc.) do airport towers use when measuring things like aiport elevation and current QNH for airport? Is there even a commonly accepted one worldwide? I couldn't find an explanation on this subject online.

The one you will find most commonly is WGS84

I've only done passing research on the matter before, so if anyone knows more please chime in.  As far as I know the FAA uses NSRS (National Space Reference System), and the NSRS currently uses NOAA GEOID models, although this is expected to be changed in 2022.  I'm not sure which regulation covers airport surveys, but you can reference AC 150/5300-18 (pdf). ICAO Annex 14 doesn't seem to mention a specific vertical datum for MSL, but specifies that, independent of the method, surveyed altitude for precision approach runways has to be accurate to "one-quarter metre or foot".
Interestingly, some airports and navaids aren't even using the WGS-84 lat/long coordinates, much less a recent international geoid model for MSL.  This is increasingly rare, but you can check a list of waypoints excluded by Garmin for non-WGS-84 compliance here and see a list of overall compliance by country here.
While it's always nice to have higher resolution MSL altitude models, we have to keep in mind their limited usefulness. Since airport's charted elevation is the reference point for barometric altitude in aviation, the only issues with an inaccurate airfield elevation are seen when comparing to elevation measured elsewhere. As a result airplanes a few miles from the airport may indicate less accurate elevation relative to the airport and local sea level (but would indicate accurately relative to other altimeters at the same location). An inaccurate survey would also affect GPS's geometric or "GLS" altitude, but that's basically only used as a cross-check.
I'd guess that in practice temperature and pressure variations over an area are greater than the variations in geoid elevation error over the area, and regulations already account for those inaccuracies, for example by requiring higher MDA when using an altimeter setting from a different airport. Additionally, some of the tools for measuring altitude on an aircraft have much lower accuracy than the <1 m accuracy of these geoid models and surveys.  Even an ideal radio altimeter can only measure 1.5 ft accuracy and then only when close to the ground (according to Arinc 707-7), and un-augmented GPS and barometric altitudes are frequently off by several dozen feet. Aviation is designed with imprecise altitude measurements so sub-foot precision isn't necessary or practical away from an airfield.

Thanks for the in-depth explanation. Do all airports use the geoid as the reference point? Is the ellipsoid not used at all in this case?

@MelihDurmaz Yes. I'm not sure why you'd ever want to use the ellipsoid height in aviation.  Geoid height is the traditional elevation on maps and tends to correspond more closely to uncorrected ISA pressure altitude than the ellipsoid. The WGS-84 ellipsoid is just a simpler construct to approximate the geoid.

That concludes my questions. Thanks again for the answer.


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What is the definition of "geometric height" referred in the ISA Model?
The International Standart Atmosphere document always mentions the "geometric height" (along with the geopotential hieght) in their calculations. I predict that it means orthometric height, which is the distance from a point in the atmosphere to the Geoid (as an approximation of the Mean Sea Level). My questions are:

Is it actually  the same as orthometric height? Is there a reliable source with the definition? I need to be certain because I am going to be using these formulas in a critical setting. There is no definition I could find in the document and other sources that I found have been unreliable.
If they are the same, why don't they use the term "altitude" instead of "height" since they're referring to the distance to Mean Sea Level and not to the Earth's surface?
If they are not the same, how are they different? And again, is there a reliable source that has the definition.

Thanks in advance.

Are you referring to the ICAO Standard Atmosphere (ICAO Doc 7488) or the U.S. Standard Atmosphere (your link). They may be very similar, but if you are looking for exact definitions you should be clear.

In the ICAO Standard Atmosphere model, as described in ICAO Doc. 7488, the geometric height is equivalent to the orthometric height.
The ISA model uses a hydrostatic equation to calculate the pressure differential over a geopotential height difference.
The reference height (0 meters) of the model is the mean sea level. It furthermore assumes a standard acceleration due to gravity, conforming to a latitude of 45.32'33". This $g_0 = 9.80665$ m/s2 is used to convert between geopotential height $H$ to geometric height $h$.
For this purpose the ISA model assumes a non-rotating earth with uniform mass distribution, so that only Newton's gravitation law can be used to obtain the relation between $H$ and $h$:
$H=\frac{rh}{r+h}$.
with $r = 6356766m$ the radius of the nominal (spherical) earth.
Now to orthometric height.
The orthometric height of a point is the distance H along a plumb line from the point to a reference height (typically the mean sea level).

Image source: ScienceDirect: Evaluation of the various orthometric height systems and the Nigerian scenario – A case study of Lagos State
The plumb line however, is not a straight line. Due to rotation of the earth and gravitational anomalies due to an irregular mass distribution in the earth, the plumb line curves.
Within the ISA model, orthometric height and geometric height are the same, because the model assumes the earth is uniform, spherical and non-rotating. Therefore the plumb line in the ISA model is straight.
In the real world however, the orthometric height (measured along the curve of the plumb line) is thus not equal to the geometric height (which measures along a straight line).
The difference are extremely small; for practical purposes this can be ignored in most fields and orthometric height is usually said to be the same as geometric height.

Well the model (in the referenced paper) does acknowledge tbat gravity includes centrifugal force due to rotation of Earth, and than dismisses the variation due to that as negligible while it does not seem to mention the curvature of the plumblines at all.

Since this answer also explains the difference between orthometric and geometric height, I will accept this as the solution.
I feel truly enlightened and I am grateful. I've been searching on this for a while now. Thank you.

@JanHudec isn't that the great thing about modelling, that freedom to simplify when you can justify it? To derive the gravity at sea level they take rotation into account. Then when deriving the relation between geopotential height and geometric height they ignore it. While at it, they also ignore the effect of the mass in the atmosphere on gravity. Then, when calculating pressure, the mass of the atmosphere is taken into account again. It may seem inconsistent but it makes perfectly sense.

Geometric height differs from your provided definition of orthometric height.

geometric altitude is the standard direct vertical distance above mean sea level

is the definition cited from your 1976 source by https://en.wikipedia.org/wiki/International_Standard_Atmosphere.

Word usage can drift over the decades (height vs. altitude).  This may be a separate, more general, question.  Section 1.2.6 and Table III of your source calls it Geometric Altitude, though.

They differ in that your source nowhere mentions the geoid, so it can't be using your definition of orthometric height.

How does “mean sea level” differ from “geoid” in your definition? Because as far as I can tell those are synonyms.

Actually, the fact that they change from "height" to "altitude" in that specific section and table only raises more concern or indicates an inconsistent usage of terminology. Not that I am in a place to hold a candle to those people.


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Relation between altimeter setting (QNH) formula and the barometric formula
I'm searching for a reliable source for a formulization of the QNH adjustment to the barometric altitude. I found this document from weather.gov that gives a formula for the Altimeter Setting, which is QNH if I'm correct. If I replace the formula's values with the appropriate constant names, it becomes this:
$Altimeter Setting (QNH?) = \left ( P - 0.3 \right )\left ( 1 + \left ( \left ( \frac{P_{0}^{\frac{L.R}{g}} L}{T_{0}} \right ) \left (  \frac{H}{\left ( P - 0.3 \right )^{\frac{L.R}{g}}}\right ) \right ) \right )^{\frac{g}{LR}}$
I also know the following formula from the US Standard atmosphere (which is identical to the ISA standard atmosphere up to 50 km):

Which can be expresses like this (for troposphere):
$P = P_{0} \left [ \frac{T_{0}}{T} \right ]^{\frac{g.M}{R.L}}$
Symbols and their meanings for extra information:

$P$: Pressure at the airport
$H$: Altitude at the airport
$P_{0}$: Standart pressure (1013.25 $hPa$)
$T_{0}$: Standart temperature (288.15 $K$)
$L$: Temperature lapse rate
$R^{*}$: Universal/ideal gas constant
$R$: Characteristic gas constant
$g$: Gravitational acceleration of Earth.
$M$: Molar mass of dry air

So, my questions are twofold:

Are these formulas actually different reperesentations of the same formula? I tried but I haven't been able to acquire the second formula from the first one.

What is the $-0.3$ for in $(P-0.3)$ in the first formula? Why is it there?

If you plug in the figures and get the same answer, or very close, the practical value is confirmed. Unless your aim is to understand the math.
I'd try some known rules of thumb like 1 hPa ~ 27 ft ie 27 ft with Std Atmosphere for the rest of the variables should lead to a stn pressure of 1014.25.

I've tried it, their results were about 5 hPas apart, which equates to about 40-50 meters of altitude difference. But I am trying to understand the math as well. If I'm gonna use this formula from weather.gov, I need to be able show where it originated from. A reliable source/formula.

Which one seems to  be most correct when compared to the ISA -- International Standard Atmosphere - Table ?

This is a quite old post but I found the same equation on weather.gov a few days ago and I asked myself the same question: where does that formula come from?
It looks like it can indeed be derived from equation (33a). For simplicity, I rewrote it with $H_b=0$ and $\frac{R}{M}=R_s$ as:
$$P = P_0\left(\frac{T_0}{T_0+LH}\right)^{\frac{g}{R_sL}}\tag{1}$$
The only difference with the equation from weather.gov is that $L$ seems to have inverted sign: so in equation (1), one should set $L=-0.0065\frac{K}{m}$ for troposphere. If we want to use $L=+0.0065\frac{K}{m}$ as weather.gov's equation seems to do, we need to rewrite (1) as:
$$P = P_0\left(\frac{T_0-LH}{T_0}\right)^{\frac{g}{R_sL}}=P_0\left(1-\frac{LH}{T_0}\right)^{\frac{g}{R_sL}}\tag{2}$$
If we solve for H (from equation 1) we get:
$$H=\frac{T_0}{L}\left[1-\left(\frac{P}{P_0}\right)^\frac{R_sL}{g}\right]\tag{3}$$
Finding the altimeter setting (given the pressure $P_A$ measured at the airport) means finding a specific pressure $P_X$ in the standard atmosphere such that if we position ourselves at the altitude where that pressure $P_X$ is found and then we go up by an amount equal to the elevation of the airport, the pressure that we find is the one that we measured at the airport, i.e. $P_A$
So the elevation of such altimeter setting in the standard atmosphere (which we'll call $H_X$) is:
$$H_X=\frac{T_0}{L}\left[1-\left(\frac{P_X}{P_0}\right)^\frac{R_sL}{g}\right]\tag{4}$$
$P_X$ is indeed what we're looking for, and $H_X$ is the elevation where pressure $P_X$ is found in the standard atmosphere.
The elevation of the airport in the standard atmosphere is instead:
$$H_A=\frac{T_0}{L}\left[1-\left(\frac{P_A}{P_0}\right)^\frac{R_sL}{g}\right]\tag{5}$$
It's worth noticing that while $P_A$ is the actual pressure we measured at the airport, $H_A$ is not the real elevation of the airport.
At this point all we need to do is to solve this equation:
$$h = H_A - H_X\tag{6}$$
where $h$ is the known actual elevation of the airport, and $H_A$ and $H_X$ are equations 4 and 5. I'll spare you the math, but it's easy to prove that (6) yields to:
$$P_X=P_A\left[1+\frac{hL}{T_0}\left(\frac{P_0}{P_A}\right)^\frac{R_sL}{g}\right]^\frac{g}{R_sL}\tag{7}$$
which is the equation you find on weather.gov, a bit rearranged.
Except it's not. I admit I don't know what that $0.3$ is for. It looks like a correction on the reading of the pressure (and 0.3 millibar is really not that much) but I have no idea where it comes from. Reducing the pressure reading by 0.3 millibar is equivalent to adding roughly 3 meters and make the altimeter setting slightly "higher".
As gszlag suggest that's to account for landing gear height.

The answer by gszlag has a different (but similar) explanation for the 0.3 mb - landing gear height.

Yes his explanation makes much more sense.

Altimeter(setting): The 0.3 mb or .01 inHg is deducted from station pressure to account for landing gear height of 10 feet.
The derivation of Altimeter and a discussion of the "landing gear offset" as I call it, can be found in the 1951 Smithsonian Meteorolgical Tables, page 269.https://repository.si.edu/handle/10088/23746
Although most might equate Altimeter = QNH, I don't think they are the same. As far as I can tell, QNH has no such offset.
To see this, try inputting an elevation along with the ISA pressure for that elevation into; https://www.weather.gov/epz/wxcalc_altimetersetting and you will see that Altimeter setting comes out to be 1012.95 or 29.91 rather than the expected 1013.25 or 29.92. It comes out short by this rather peculiar elevation offset.

Formula 33a (from the US Standard Atmosphere 1976 document you quote) gives you the pressure at a specific altitude in the U.S. Standard Atmosphere, and corresponds closely to airport/station level pressure in met reports (it corresponds exactly when the real atmosphere has the same characteristics as the Standard Atmosphere). An altimeter setting/QNH is essentially a pressure at sea level (and will be 29.92"Hg/1013.2HPa when the real atmosphere matches the Standard Atmosphere, no matter what elevation the airport is).
see the weather.gov definitions here
So the two formulas (33a, and the weather.gov formula you quote) do not give the same thing.
It would be interesting to know why you need to calculate an altimeter setting, as opposed to getting it from met reports. The setting provided in met reports is a value calculated from the measured station level pressure, and this calculation is actually non-trivial.
Beware the frequently-used rule-of-thumb of 27 feet being equal to 1 HPa on an altimeter is only an approximation, and one which only "works" for low elevations/altitudes.

Two formulas do not calculate the same values, yes. But they use the same constants and variables. So I thought maybe you could extract one from the other. I don't know the exact mathematical term.
If they are different formulas, I need to find where the altimeter setting formula originates from.
This is project that I work in, and one that needs proof for solutions. It's interesting that altough non-trivial, this calculation is used worldwide but it's very difficult to find how it is done.

@MelihDurmaz You were asking whether they are "different representations of the same formula", and they are not, even though some of the terms are similar (Note the absence of temperature T at the aerodrome in the equation for QNH). Based on your comment, I suspect you may really be looking for the (non-trivial) formula for reducing station level pressure to sea level to determine QNH. Perhaps try searching those terms, you will find quite a few results.


text:
Can a quadcopter fly stable while its all 4 motors from different manufacturers?
What if we used 4 motors which all are from different manufacturers? Will it fly/hover ? All 4 brushless motors have same kv and dimensions. Like 2204 2300kv .

I would think it would depend more on the output power than manufacturer or dimensions...

Shouldn't be a problem except the tuning of the control loop might be difficult

You might get more practical answers on a site like rc groups dot com.


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What are Uses of thin airfoil and thick airfoil?
I have heard that thin airfoils are used for fast fyling and thick airfoil a are used for more lift. Is it true? Can you explain specific uses of thick and thin airfoils ?

Thick, cambered airfoils such as the Gottingen, Clarke Y and Davis are the most efficient airfoils up to speeds where Mach number becomes critical.
Lift is determined by the lift formula:
$Lift$ =  1/2 × Coefficient of Lift × Air density × Wing Area × Velocity$^2$
Coefficient of Lift can be further broken down into Angle of Attack and Airfoil type.
So a smart designer picks the most efficient airfoil and the least amount of area required
to lift a given weight.
Now time to choose.  By virtue of Bernoulli, the highest lift to drag ratios are achieved by accelerating air over the top of the wing.  This is where thick wings shine, much to the amazement of aircraft designers 100 years ago.  Thick wings also have gentle stalling characteristics, helping make the Fokker D.VII a real hit in 1918.  The thickness also enabled internal cantilever construction instead of bracing wires, paving the way for higher speeds until...
Higher airflow velocity above the wing approached trans sonic speeds, which lead to an increase in drag.  This forced designers to give up the top lift and use bottom lift, where the airflow is slower. That lead to the "supercritical" wing for high subsonic cruise.  Super critical wings feature a very "flat" upper surface.  Note airliners drasticly increase camber for slower phases of flight with retractable slats and flaps.
Supersonic aircraft wings are thin to avoid drag, but can create lift with a swept leading edge, much like a paper air plane.  This type of lift is called vortex lift.  As seen from the formula above, Velocity is squared.  This means that at high speeds, the wing need not be as efficient to generate the desired lift, as seen in designs such as the Concorde.
Of course, with very little weight, like a paper airplane, it works too.

This is true for most cases, because thin airfoils normally produce less drag and less lift than thick ones at the same angle of attack. But they are also exceptions.
Thick airfoils, to be specific Supercritical airfoil, are commonly used by commercial airliners, but not only because they could produce less drag. Airlinears fly at speed which shock wave could emerge at the upper surface of the wing, which produces additional drag. The solution to this is to make the upper surface of the airfoil flat, but at the same time lift was reduced. In order to produce enough lift, the lower surface of the airfoil have to be complex, which guarantees a thick airfoil. These airfoils have high lift-drag ratio, which is crucial to airliners.
Thin airfoils are commonly used by supersonic aircrafts. Experiment shows that airfoli which of 6 % relative thichness produces almost twice drag than a airfoil of 4% relative thickness. At the same time, thickness have negligible effect on lift for thin airfoils in supersonic speeds.